After a two-hour hearing on Thursday, Judge Robertson declined to block the trial. In a statement from the bench he said that under the military commission system set up by Congress and the White House, Mr. Hamdan's lawyers must wait until a final verdict in the trial before raising their constitutional challenges.

A military judge at Guantánamo had earlier rejected similar arguments from Hamdan's lawyers.

Judge Robertson's decision not to delay the trial marks a victory for the Bush administration in its effort to build legitimacy for its controversial legal approach to the war on terror.

Military officials have been pushing hard – despite a string of legal setbacks – to conduct several war crimes trials this year.

Hamdan is facing trial on terror conspiracy and material support charges. His lawyers had urged Judge Robertson to postpone the military tribunal to allow Hamdan a new round of legal challenges.

The case was being closely watched because it could have greatly increased the constitutional protections applicable not only in Hamdan's trial, but also in the trial of alleged 9/11 mastermind Khaled Shaikh Mohammed and other Al Qaeda leaders.

The Bush administration's military commission process has sparked condemnation by critics in the US and overseas. They say it is rigged to produce convictions by allowing hearsay evidence coerced during harsh interrogations.

Administration officials defend the special military commission process as a necessary innovation to wage the war on terror without jeopardizing sensitive intelligence sources and methods.

The Hamdan hearing was among an array of cases moving forward in the wake of the Supreme Court's June 12 decision extending certain constitutional protections to terror suspects at Guantánamo.

Federal judges in Washington are gearing up to hear scores of habeas corpus petitions challenging the legality of their open-ended detention at the terror prison camp.

While the Supreme Court made clear that habeas protections cover detainees at Guantánamo, the justices left it to the lower courts to define the scope of those protections and to work out the details of how to apply them in individual cases.

In the Hamdan case, government lawyers argued that habeas protections at Guantánamo apply only to detainees who have not been charged with war crimes. Of the 265 Guantánamo detainees, 19 – including Hamdan - have been charged as war criminals.

"The purpose of constitutional habeas is to test the legality of detention, not to challenge a trial in advance," wrote Justice Department lawyer Alexander Haas, in the government's brief to Judge Robertson.

"The ability to try alien enemy combatants suspected of war crimes in a timely fashion is an important part of the United States' war effort, and the public has a strong interest in seeing such individuals brought to justice as soon as possible," Mr. Haas wrote. "For this Court to enjoin the ongoing military commission process now ... would harm those significant interests as well as undermine the separation of powers principle that is so fundamental to our government."

Hamdan's lawyers said their client should enjoy the same legal safeguards as other detainees at Guantánamo.

"The Government notes that the public has a strong interest in the prompt, effective, and efficient administration of justice. Hamdan could not agree more," wrote Hamdan's lawyer Neal Katyal, in his brief to the judge. "But ... rushing to try him just weeks after the Supreme Court has upended the foundations for his commission and acknowledged his right to habeas will lead to confusion, inefficiencies, and uncertainty."

Mr. Katyal and Judge Robertson had been in this position before. In 2004, Katyal, a law professor at Georgetown Law Center in Washington, argued that the military commission process violated essential legal safeguards. Judge Robertson agreed and struck down the commissions. An appeals court reversed the decision, but the US Supreme Court ultimately ruled in Hamdan's favor.

That prompted the Bush administration and Congress to pass the Military Commissions Act of 2006 in defiance of the Supreme Court's ruling. On June 12, the high court responded by striking down a key portion of the MCA.

Although Hamdan was not a party in that case, the decision is consistent with legal positions staked out by his lawyers.

In Thursday's hearing the question was whether Hamdan would benefit from the high court victory.

"All he wants is a fair trial," Katyal wrote in his brief.

"If individuals merely being detained have a right to challenge their detention, then detainees who are set to be tried must have an even stronger right to challenge a trial that may result in life imprisonment or death," Katyal said in his brief.

Hamdan, a Yemen national, was captured in Afghanistan in November 2001. He is accused of plotting with Al Qaeda to murder US military personnel. The charge is based on the presence of SA-7 surface-to-air missiles in his car at the time he was captured.

Hamdan says he was not a member of Al Qaeda or a supporter of Mr. bin Laden, merely his employee. Military lawyers say Hamdan was delivering the missiles to Al Qaeda fighters during active hostilities near Takta Pol, Afghanistan, for use against US forces. They say he also served as a driver and bodyguard to bin Laden.

If convicted, Hamdan could face life in prison.

The central issue in the Hamdan hearing before Judge Robertson was whether he should be permitted to apply constitutional standards to challenge the commission process in pre-trial motions.

Hamdan's lawyers said his commission trial violated several constitutional protections and that the lawyers must be permitted to litigate those issues before a trial takes place.

Government lawyers said the MCA requires that all appeals by a defendant be postponed until after any conviction.

Katyal argued that the conspiracy and material support charges filed against Hamdan are not war crimes, and their adoption by Congress as war crimes after Hamdan's capture violated the Constitution's ex post facto clause. He said the military commission process violated Hamdan's right to equal protection and due process, and did not comply with the Geneva Conventions.

Government lawyers said the military commission process was created by Congress and features an impartial judge and jury, as well as a "full panoply" of trial rights.

"Such rights for an alien charged with war crimes are utterly unprecedented and far exceed the protections given to the defendants [in prior war crimes tribunals]," Haas said.